Electrolytic process of forming hydrazine



July 1, 1958 J. F. HALLER 2,841,543

ELECTROLYTIC PROCESS OF FORMING HYDRAZINE Filed Oct. 20, 1953 GAS SOLUTION 24 CATHODE 22 ANODE (ponous) ELECTROLYZED sownou John F. Holler IN VEN TOR.

ATTORNEYS United States Patent ELECTROLYTIC PROCESS OF FORMING HYDRAZINE John F. Haller, Niagara Falls, N. Y., assignor m Olin Mathieson Chemical Corporation, a corporation of Virginia Application October 20, 1953, Serial No. 387,244

5 Claims. (Cl. 204-59) My invention relates to a novel method for forming hydrazine by the electrolysis of solutions of liquid ammonia containing electrolytes utilizing an electrolytic cell containing a porous anode.

Liquid ammonia, like water, when pure, is a poor electrical conductor. To the extent that ammonia ionizes, however, it is a source of ammonium and amide ions:

Electrolysis of liquid ammonia, intending the discharge of the amide ions at the anode and their combination to form hydrazine has been proposed but no successful method has been devised.

I have now found that electrolysis of solutions of liquid ammonia containing electrolytes soluble in liquid ammonia can be utilized to form hydrazine. I have found that electrolyzing such solutions in an electrolytic cell containing a porous anode produces anhydrous hydrazine. According to the method of my invention, a solution of liquid ammonia containing an electrolyte soluble in liquid ammonia is prepared and electrolyzed in an electrolytic cell containing a porous anode. The solution is forced through the porous anode by any suitable means, for example, by gravity, by reduced pressure on the eflluent side or by increased pressure on the side towards the cathode. Hydrazine in anhydrous form is thenseparated in any convenient manner from the electrolyzed solution, for example, by distillation. Advantageously, in the recovery of the hydrazine from the solution, ammonia is recovered and recycled to the process. Thus, the method of my invention provides a novel method of producing hydrazine by the electrolysis of liquid ammonia solutions.

The electrolytes sutficiently soluble in liquid ammonia which are useful in my invention include, for example, sodamide, sodium hydroxide, water, ammonium salts including ammonium nitrate, ammonium sulfamate and urea. The electrolytes must be non-reactive with the components of the system.

The process of my invention will be further illustrated by reference to the accompanying drawing, which illustrates a particularly advantageous form of electrolytic cell useful according to my invention.

In the drawing, the cell comprises a top and bottom section made of glass, between which two electrodes are clamped, using polyethylene gaskets for separation. The top section of the cell is bell-shaped and terminates at a tubulature 11, which serves as an outlet for gas formed. The top section 10 also contains a side tubulature 12, which serves as an inlet for the solution to be electrolyzed. The top section terminates at its lower edge in a flange 13 to which is applied a polyethylene ring 14 as a gasket. A perforated metal cathode plate 15 closes the top section of the cell. A second polyethylene ring 16 separates the perforated cathode from the porous anode 17. The porous anode 17 is separated from the bottom of the cell by a polyethylene ring 18. The bottom of the cell is closed by a circular glass bottom section 19 having a. central tubulature 20. An upper ring 21 of metal and p 2,841,543 Patented July 1, 1958 a lower ring 22 of metal are held together by threaded pins 23 and nuts 24, completing the cell assembly.

In operation, suitable connections are made to tubu-- latures 11, 12 and 20, and the cell is maintained at the desired temperature for maintaining the ammonia in liquid form, for example, by immersing the cell in a low tem perature bath. A solution of liquid ammonia containing. an electrolyte is introduced through tubulature 12, a suit able electromotive force is applied and any gas generated in the cell flows out through tubulature 11. Electrolyzed solution passes, for example, by gravity, through the porous electrode 17 and is removed from the cell by tubulature 20. The removed solution is then treated to recover hydrazine and ammonia, which is recycled to the process.

While the above described cell is a particularly advantageous type of cell, any suitable electrolytic cell containing a porous anode may be used in the process. Multiple sets of cathodes and anodes may also be used. The perforated metal cathode may be constructed of iron or stainless steel or other suitable metals. The porous anode may be constructed of stainless steel, preferably of a porosity of H, i. e. a mean pore-opening of 5 microns, but other materials such as nickel, gold, platinum or carbon may also be used.

It appears that in the electrolysis, if the hydrazine formed remains in the vicinity of the anode, the hydrazine is decomposed. Since the reaction is an electrochemical oxidation of ammonia to hydrazine and hydrazine is more susceptible to oxidation than ammonia, the hydrazine is quickly destroyed. By conducting the electrolysis of liquid ammonia solutions containing an electrolyte in an electrolytic cell containing a porous anode and controlling the voltage gradient and the flow rate of the solution, however, the hydrazine formed is carried through the anode in the ammonia solution and removed immediately from the vicinity of the anode and decomposition is effectively avoided. In the operation of the cell, a potential gradient is applied such that cations are repelled by the anode at a velocity greater than the flow rate of the solution through the porous anode so that the anion, i. e., amide ion, is passed selectively through the porous anode at which it forms hydrazine which is immediately removed by the flow of solution.

The process of my invention will be further illustrated by reference to the following examples.

Example I A porous electrode cell similar to that shown in the accompanying drawing was immersed in a bath of acetone, cooled, by the addition of Dry Ice, to a temperature of -36 C. A solution of sodamide in liquid ammonia was prepared from metallic sodium using iron as a catalyst. The solution was then flowed through the cell while a current varying from 9.7 to 12.3 milliamperes was applied at a voltage of about 6 volts. After operation for 32 minutes, liquid ammonia was allowed to evaporate from the eflluent solution over night. A sample of the residue was treated with 4 ml. of a hydrazine reagent prepared by adding 2 grams of paradimethylaminobenzaldehyde and 10 ml. of concentrated hydrochloric acid to ml. of absolute alcohol. The treated solution acquired a dark red color and subsequently a precipitate formed indicating a positive test for the formation and presence of hydrazine.

Example II the hydrazine reagent, a strong red coloration was formed 7 indicating the production of hydrazine.

Example III A solution of liquid ammonia saturated with water at -36 C. was passed through the cell of Example I while a current varyingfrom about 50 to 65 milliamperes flowed through the cell at 33 volts for 40 minutes. The effluent cell liquor was evaporated over night at atmospheric pressure and temperature. Potassium iodate solution added to the residue dissolved in water and acidified showed the presence of hydrazine.

Example 1V Solid pellets of sodium hydroxide were added to saturate liquid ammonia which was then introduced into the porous electrode cell of Example I. A current varying from 5 to 65 milliamperes at about 33 volts was passed through the electrolyte for 23 minutes. The electrolyte was evaporated as in Example I. Addition of potassium iodate solution to the acidified electrolyte indicated that hydrazine was present in the solution.

Example V A mixture of 1 ml. of 50 percent sodium hydroxide solution and 100 ml. liquid ammonia Was prepared and passed through the cell of Example I. At -36 (3., a current of about 11 to 18 milliamperes was passed through the electrolyte at about 33 volts for 43 minutes. Potassium iodate titration of a sample of the acidified electrolyte showed the presence of hydrazine in the product.

I claim:

1. A process of forming hydrazine which comprises electrolyzing a solution of liquid ammonia containing an electrolyte soluble in liquid ammonia in an electrolytic cell containing a porous anode comprising a conductive material selected from the group consisting of stainless steel, nickel, gold, platinum and carbon while forcing the solution through the porous anode and applying a potential gradient to the cell sufiicient to repel cations of the solution at the anode at a velocity greater than theflow rate of the solution through the porous anode and re covering hydrazine from the electrolyzed solution.

2. A process of forming hydrazine which comprises electrolyzing a solution of liquid ammonia containing sodamide in an electrolytic cell containing a porous anode comprising a conductive material selected from the group consisting of stainless steel, nickel, gold, platinum and carbon while forcing the solution through the porous anode and applying a potential gradient to the cell sufiicient to repel cations of the solution at the anode at a velocity greater than the flow rate of the solution through the porous anode and recovering hydrazine from the electrolyzed solution.

3. A process of forming hydrazine which comprises.

electrolyzing a solution of liquid ammonia containing water in an electrolytic cell containing a porous anode comprising a conductive material selected from the group consisting of stainless steel, nickel, gold, platinum and carbon while forcing the solution through the porous anode and applying a potential gradient to the cell sufficient to repel cations of the solution at the anode at a velocity greater than the flow rate of the solution through the porous anode and recovering hydrazine from the electrolyzed solution.

4. A process of forming hydrazine which comprises electrolyzing a solution of liquid ammonia containing sodium hydroxide in an electrolytic cell containing a porous anode comprising a conductive material selected from the group consisting of stainless steel, nickel, gold, platinum and carbon while forcing the solution through the porous anode and applying a potential gradient to the cell suflicient to repel cations of the solution at the anode at a velocity greater than the flow rate of the solution through the porous anode and recovering hydrazine from the electrolyzed solution.

5. The process of claim 1 in which the anode is made of stainless steel.

References Cited in the file of this patent UNITED STATES PATENTS Hulin July 13, 1897 OTHER REFERENCES 

1. A PROCESS OF FORMING HYDRAZINE WHICH COMPRISES ELECTROLYZING A SOLUTION OF LIQUID AMMONIA CONTAINING AN ELECTROLYTE SOLUBLE IN LIQUID AMMONIA IN AN ELECTROLYTIC CELL CONTAINING A POROUS ANODE COMPRISING A CONDUCTIVE MATERIAL SELECTED FROM THE GROUP CONSISTING OF STAINLESS STEEL, NICKEL, GOLD, PLATINUM AND CARBON WHILE FORCING THE SOLUTION THROUGH THE POROUS ANODE AND APPLYING A POSOLUTION AT THE ANODE AT A VELOCITY GREATER THAN THE FLOW RATE OF THE SOLUTION THROUGH THE POROUS ANODE AND RECOVERING HYDRAZINE FROM THE ELECTROLYZED SOLUTION. 